System and method for extracting carbon dioxide from atmospheric air via pressure-swing absorption

ABSTRACT

One variation of a method for carbon sequestration includes: mixing ambient air including carbon dioxide and secondary gases with a working fluid to generate a first mixture; conveying the first mixture through a compressor to pressurize the first mixture from a first pressure to a second pressure greater than the first pressure to promote absorption of carbon dioxide into the working fluid; depositing the first mixture in a high-pressure vessel to generate an exhaust stream of secondary gases and a second mixture including carbon dioxide dissolved in the working fluid; conveying the second mixture through a turbine configured to extract energy and reduce pressure of the second mixture, from the second pressure to the first pressure, to promote desorption of carbon dioxide from the working fluid; transferring the second mixture into the low-pressure vessel; and releasing carbon dioxide, desorbed from the working fluid, from the low-pressure vessel for collection.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/925,721, filed on 24 Oct. 2019, U.S. Provisional Application No.62/985,759, filed on 5 Mar. 2020, and U.S. Provisional Application No.63/072,332, filed on 31 Aug. 2020, each of which is incorporated in itsentirety by this reference.

TECHNICAL FIELD

This invention relates generally to the field of carbon sequestrationand more specifically to a new and useful system and method forpressure-swing absorption of carbon dioxide in the field of carbonsequestration.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic representation of a system;

FIG. 2 is a schematic representation of the system;

FIG. 3 is a flowchart representation of a method;

FIG. 4 is a flowchart representation of a method; and

FIG. 5 is a schematic representation of the system.

DESCRIPTION OF THE EMBODIMENTS

The following description of embodiments of the invention is notintended to limit the invention to these embodiments but rather toenable a person skilled in the art to make and use this invention.Variations, configurations, implementations, example implementations,and examples described herein are optional and are not exclusive to thevariations, configurations, implementations, example implementations,and examples they describe. The invention described herein can includeany and all permutations of these variations, configurations,implementations, example implementations, and examples.

1. Method

As shown in FIGS. 3 and 4, a method S100 for carbon sequestrationincludes: mixing ambient air including carbon dioxide and a set ofsecondary gases with a working fluid from a low-pressure vessel 130 togenerate a first mixture including a volume of air dispersed throughoutthe working fluid in Block S110; conveying the first mixture through acompressor 120 configured to pressurize the first mixture from a firstpressure within a first pressure range at an inlet of the compressor 120to a second pressure within a second pressure range at an outlet of thecompressor 120, the second pressure range greater than the firstpressure range, to promote absorption of carbon dioxide present in thevolume of air into the working fluid in Block S120; depositing the firstmixture in a high-pressure vessel no to generate an exhaust streamincluding the set of secondary gases present in the volume of air and asecond mixture including carbon dioxide dissolved in the working fluidin Block S130; and releasing the exhaust stream from the high-pressurevessel 110 via an exhaust outlet in Block S140.

The method S100 further includes: conveying the second mixture from thehigh-pressure vessel 110 through a turbine 140 configured to extractenergy from the second mixture and reduce the pressure of the secondmixture, from the second pressure at an inlet of the turbine 140 to thefirst pressure within the first pressure range at an outlet of theturbine 140, to promote desorption of carbon dioxide from the workingfluid in Block S150; transferring the second mixture from the turbine140 into the low-pressure vessel 130 in Block S160; and releasing carbondioxide, desorbed from the working fluid, from the low-pressure vessel130 for collection in Block S170.

2. System

As shown in FIGS. 1 and 2, a system 100 includes: a venturi 112; acompressor 120; a motor 150; a high-pressure vessel 110; an exhaustoutlet 134; a turbine inlet 138; a turbine 140; a low-pressure vessel130; and a collection outlet 160.

The venturi 112 is configured to mix ambient air with a workingfluid—stored in the low-pressure vessel 130—to generate a first mixtureincluding: a liquid phase including a volume of the working fluid; and agaseous phase including a volume of air dispersed within the liquidphase, wherein the volume of air includes carbon dioxide and a set ofsecondary gases.

The compressor 120: is mechanically coupled to a driveshaft 152; and isconfigured to pressurize the first mixture from a first pressure in afirst pressure range at an inlet of the compressor 120 to a secondpressure within a second pressure range at an outlet of the compressor120, wherein the second pressure range is greater than the firstpressure range, to promote absorption of carbon dioxide present in thegaseous phase into the working fluid in the liquid phase.

The motor 150 is mechanically coupled to the driveshaft 152 and isconfigured to drive the compressor 120.

The high-pressure vessel 110 is configured to receive the first mixture,at the second pressure, from the compressor 120.

The exhaust outlet 134 is configured to collect an exhaust stream,including the set of secondary gases separated from the liquid phase ofthe first mixture, from the high-pressure vessel 110.

The turbine inlet 138 is configured to collect a secondmixture—including the working fluid and a volume of carbon dioxide—fromthe high-pressure vessel 110.

The turbine 140 is mechanically coupled to the driveshaft 152 and isconfigured to: reduce the second mixture exiting the high-pressurevessel 110 from the second pressure at the turbine inlet 138 to thefirst pressure at an outlet of the turbine 140 by extracting energy fromthe second mixture; promote desorption of the volume of carbon dioxidefrom the volume of working fluid; and transfer energy extracted from thesecond mixture into a torque on the driveshaft 152 to rotate thecompressor 120.

The low-pressure vessel 130 is configured to promote separation of thevolume of carbon dioxide from the volume of working fluid of the secondmixture.

The collection outlet 160 is configured to collect the volume of carbondioxide from the low-pressure vessel 130.

3. Applications

Generally, as shown in FIGS. 1-4, the method S100 can be executed by asystem 100: to directly capture an air stream including carbon dioxideand other secondary gases found in air (e.g., nitrogen, oxygen, argon)from an air source (e.g., outdoor air, recirculated air within abuilding); to entrain a working fluid stream with this air stream togenerate a gas-liquid mixture; to process this gas-liquidmixture—according to various techniques and/or in combination withadditional components—to rapidly increase concentration of carbondioxide in the working fluid stream for removal of secondary gases fromthe gas-liquid mixture; and to rapidly separate carbon dioxide from theworking fluid stream for collection. In particular, the method S100includes: mixing an air stream including carbon dioxide and othersecondary gases with a working fluid stream to form an aspirated fluidstream; compressing this aspirated fluid stream to rapidly increaseconcentration of carbon dioxide dissolved in the working fluid streamvia pressurization of the stream; separating the secondary gases fromthe working fluid stream including the dissolved carbon dioxide in ahigh-pressure vessel 110; expanding the remaining working fluid streamand dissolved oxygen to rapidly decrease concentration of carbon dioxidedissolved in the working fluid stream via depressurization of the fluidstream; and separating the gaseous carbon dioxide from the working fluidstream in a low-pressure vessel 13 o. This gaseous carbon dioxide canthen be collected and stored while the working fluid can be recycled tocontinuously extract carbon dioxide from an inbound air stream. Forexample, the method S100 can be executed to extract carbon dioxide fromatmospheric air and sequester this carbon dioxide via anenergy-efficient (e.g., high energy recovery), scalable, deployable, andcost-effective process.

Traditional systems and/or processes for capturing carbon dioxide fromatmospheric air operate with substantial energy losses, are notscalable, and are not cost-effective. Conversely, the system 100consumes significantly less energy (e.g., 40 percent less energy) thantraditional carbon capture systems by implementing methods andtechniques for recapturing energy supplied to the system 100. Forexample, the system 100 can include: a singular driveshaft 152 coupledto a motor 150; a compressor 120 powered by the motor 150 and configuredto compress fluids for absorption of carbon dioxide into a workingfluid; and a turbine 140 configured to expand fluids for desorption ofcarbon dioxide from the working fluid. The motor 150 can be configuredto supply power to the compressor 120. However, at the turbine 140,high-pressure, high-energy carbon dioxide is expanded to lower-pressure,lower-energy carbon dioxide. This energy gained by the system 100 fromthe expansion of carbon dioxide can be converted to mechanical energy.Because the turbine 140 and the compressor 120 are coupled to the samedriveshaft 152, this mechanical energy generated by the turbine 140 canbe leveraged to power the compressor 120, thus reducing energy requiredby the motor 150 to power the compressor 120. Further, by mechanicallycoupling the compressor 120, the turbine 140, and the motor 150 to asingular driveshaft 152 extending along a central axis of thelow-pressure vessel 130, the system 100 is limited to a singular movingassembly, thereby: minimizing opportunities for breakage of differentparts of the system 100; minimizing a number of parts required forassembly of the system 100; and increasing compactness and spaceefficiency of the system 100.

Furthermore, because the system 100 includes few moving parts and isscalable, the system 100 can be deployed to various locations to capturecarbon dioxide from atmospheric air at these various locations. Forexample, the system 100 can be deployed as a modular unit anddistributed about a large geographic region to sequester carbon dioxidefrom atmospheric air in this geographic region. In another example, thesystem 100 can be mounted to a building or structure. In each of theexamples, the system 100 can be scaled to an appropriate size based onthe location of deployment.

The system 100 is configured to capture carbon dioxide from atmosphericair by leveraging solubility of carbon dioxide in the working fluid(e.g., water) at different pressures. In particular, the system 100 isconfigured to: concentrate carbon dioxide in the working fluid andseparate out secondary gases at high pressures in a high-pressure vessel110; and separate carbon dioxide from the working fluid at low pressuresin a low-pressure vessel 130 (e.g., after secondary gases have beenremoved). Therefore, by oscillating the working fluid between twovessels (e.g., a high-pressure vessel 110 and a low-pressure vessel130), the system 100 can leverage changes in pressure to control acarbon dioxide carrying capacity of the working fluid and thus controlabsorption and desorption of carbon dioxide form the working fluid.

4. Nested High-Pressure & Low-Pressure Vessels

In one implementation, as shown in FIG. 1, the system 100 includes: alow-pressure vessel 130 configured to hold fluid at pressures within afirst pressure range; and a high-pressure vessel 110—nested within thelow-pressure vessel 130—configured to hold fluids at pressures within asecond pressure range exceeding pressures within the first pressurerange. Generally, in this implementation, the high-pressure vessel 110and the low-pressure vessel 130 are coextensive. Further, thehigh-pressure vessel 110 and the low-pressure vessel 130 are structuraland can therefore carry secondary components of the system 100. In thisimplementation, because the high-pressure and low-pressure vessels 110,130 are nested and structural, the vessels, valves, driveshaft, andother elements of the system 100 can be arranged in a compactconfiguration with a single moving element, thereby: limiting featuresprojecting outwardly from a body of the system 100 defined by thelow-pressure vessel 130; limiting the overall diameter of the system 100(e.g., to a diameter of the low-pressure vessel 130) per unit mass orvolume flow rate of ambient air through the system 100 (and thereforemass rate of carbon dioxide captured by the system 100); increasingcompactness and space efficiency of the system 100 per unit mass orvolume flow rate; reducing weight of the system 100 by supportingstructures on a shell (exhibiting high hoop strength) defined by thelow-pressure vessel 130; and improving ease of storage, transport, andsetups of the system 100.

In this implementation, the system 100 further includes: a motor 150external the low-pressure vessel 130 and mechanically coupled to adriveshaft 152 extending through the low-pressure vessel 130 (e.g.,along a central axis of the low-pressure vessel 130); a compressor 120nested within the low-pressure vessel 130 and mechanically coupled tothe driveshaft 152; and a turbine 140 nested within the low-pressurevessel 130, mechanically coupled to the driveshaft 152 below thecompressor 120, and fluidly coupled to the compressor 120. Bymechanically coupling the compressor 120, the turbine 140, and the motor150 to a singular driveshaft 152 extending along a central axis of thelow-pressure vessel 130, the system 100 is limited to a singular movingassembly thereby minimizing points of failure within the system 100 andminimizing opportunities for breakage of different parts of the system100. Further, the system 100 can leverage energy recaptured by theturbine 140 via expansion of fluids to generate a torque on thedriveshaft 152 and therefore rotate the compressor 120, thereby reducingenergy required to be input by the motor 150 to rotate the compressor120.

4.1 Working Fluid+Air (Entrainment)

Block S110 of the method S100 recites mixing ambient air includingcarbon dioxide and a set of secondary gases with a working fluid from alow-pressure vessel 130 to generate a first mixture including a volumeof air dispersed throughout the working fluid. In particular, a volumeof the working fluid can be entrained with a volume of ambient air, suchthat the resulting first mixture defines: a liquid phase including thevolume of the working fluid; and a gaseous phase including the volume ofair dispersed throughout the volume of the working fluid in the liquidphase.

In one implementation, air—including carbon dioxide and other secondarygases (e.g., nitrogen, argon)—is drawn in from an external source (e.g.,a surrounding environment) via a venturi 112. The air travels through anair inlet (e.g., an enclosed air inlet) extending from a surroundingenvironment into the low-pressure vessel 130 and toward the venturi 112,such that the air does not mix with the working fluid present in thelow-pressure vessel 130 while travelling through the enclosed inlet.Simultaneously, a working fluid is drawn into an opening from thelow-pressure vessel 130 and through the venturi 112 where it is mixedwith the air.

For example, a volume of air can be drawn, from an external source(e.g., atmospheric air), through an air inlet via a venturi 112 nestedwithin the low-pressure vessel 130. Simultaneously, a volume of water(i.e., the working fluid) can be drawn through a compressor inlet 114via a compressor 120, the compressor inlet 114 fluidly coupled to theventuri 112 and the compressor 120. The volume of air—including carbondioxide and a set of secondary gases (e.g., nitrogen, argon, oxygen)—canthen be mixed with the volume of water in the compressor inlet 120 priorto reaching the compressor 120. When mixed, the volume of air and thevolume of water generate a first mixture (e.g., a gas-liquid mixture)including: a liquid phase including the volume of water; and a gaseousphase including a volume of air (e.g., of carbon dioxide and the set ofsecondary gases) distributed throughout the volume of water of theliquid phase.

The working fluid can be selected based on absorbency of carbon dioxideand other secondary gases present in atmospheric air in the workingfluid. For example, the working fluid can be configured to absorb carbondioxide at higher pressures and to release carbon dioxide at lowerpressures. Further, the working fluid can be configured to prioritizeabsorption of carbon dioxide over other secondary gases at particularpressures and temperatures, such that the working fluid selectivelyabsorbs carbon dioxide and limits absorption of (e.g., does not absorb)secondary gases present in air. In one implementation, the working fluidcan be water. In another implementation, to enable further absorption ofcarbon dioxide from the volume of air into the working fluid, theworking fluid can be treated with solvents configured to increase carbondioxide absorption. For example, the working fluid can include an aminesolvent (e.g., an ethanolamine) dissolved in water.

4.2 Pressurizing the First Mixture

Block S120 of the method S100 recites conveying the first mixturethrough a compressor 120 configured to pressurize the first mixture froma first pressure within a first pressure range at an inlet of thecompressor 120 to a second pressure within a second pressure range at anoutlet of the compressor 120, the second pressure range greater than thefirst pressure range, to promote absorption of carbon dioxide present inthe volume of air into the working fluid. In particular, the compressor120 can be configured to receive the first mixture at a first pressureand output the first mixture at a second pressure greater than the firstpressure. As pressure of the first mixture increases along thecompressor 120, a capacity of the working fluid for absorbing carbondioxide increases, thus enabling an increase in concentration of carbondioxide in the working fluid in the liquid phase.

Further, to prevent absorption of other secondary gases present in thefirst mixture into the working fluid, the system 100 can be configuredto hold the first mixture at temperatures within a particulartemperature range in which the working fluid selectively absorbs carbondioxide over other secondary gases. For example, the system 100 caninclude water as the working fluid. At temperatures exceeding 35 degreesCelsius, water may absorb carbon dioxide at significantly higher rates(e.g., 90 percent to 100 percent higher) than other secondary gasespresent in air in the first mixture (e.g., Nitrogen, Argon). Therefore,in this example, the system 100 can be configured to maintain the firstmixture at temperatures above 35 degrees Celsius and below a maximumtemperature (e.g., 45 degrees Celsius) at which carbon dioxide issignificantly less soluble in water.

In one implementation, the compressor 120 can be configured toisothermally compress air present in the first mixture, therebyincreasing pump efficiency. For example, as gases (e.g., carbon dioxide,nitrogen, argon) present in air within the first mixture are compressed,temperatures of these gases increase. However, this generated heat canbe transferred to the working fluid nearly instantaneously, such thatthe gases maintain approximately (e.g., within 2 degrees Celsius)constant temperatures. To prevent the working fluid from heating above amaximum temperature, the system 100 can include a heat exchanger coupledto the compressor 120 and configured to maintain temperatures of theworking fluid within a particular temperature range (e.g., between 35degrees Celsius and 40 degrees Celsius).

4.3 Separation of Non-CO₂ Gases

Block S130 of the method S100 recites depositing the first mixture in ahigh-pressure vessel 110 to generate an exhaust stream including the setof secondary gases present in the volume of air and a second mixtureincluding carbon dioxide dissolved in the working fluid. In particular,the high-pressure vessel 110 can be fluidly coupled to the compressor120 such that the compressor 120 transfers the first mixture into thehigh-pressure vessel 110 at elevated pressures due to compression of thefirst mixture by the compressor 120. The high-pressure vessel 110 can beconfigured to maintain these elevated pressures and/or to furtherincrease pressure of the first mixture within the high-pressure vessel110.

The high-pressure vessel 110 (e.g., a high-pressure chamber) can benested within the low-pressure vessel 130 (e.g., a low-pressurechamber). For example, the high-pressure vessel 110 can define: a seconddiameter less than a first diameter of the low-pressure vessel 130; anda second height less than a first height of the low-pressure vessel 130.In this example, the low-pressure vessel 130 and the high-pressurevessel no can be concentric the driveshaft 152 of the motor 150, suchthat the first mixture travels vertically from the compressor 120 intothe high-pressure vessel 110.

In one implementation, the system 100 includes a high-pressure vessel110 (i.e., the high-pressure vessel no) defining an upper region andlower region. The upper region can include an exhaust outlet throughwhich secondary gases separated from the working fluid can exit thehigh-pressure vessel 110. The lower region can include an outlet throughwhich the working fluid and dissolved carbon dioxide (i.e., the secondmixture) can exit the high-pressure vessel 110. Therefore, thehigh-pressure vessel 110 can be configured to: separate and accumulatethe gaseous phase of the first mixture in the upper region of thehigh-pressure vessel 110; and separate and accumulate the liquid phaseof the first mixture in the lower region of the high-pressure vessel110. Once the secondary gases have been removed (e.g., below aparticular concentration), the resulting exhaust stream can be releasedvia the exhaust outlet and the resulting second mixture can exit thehigh-pressure reactor via the outlet.

In one implementation, the high-pressure vessel 110 includes a structure152 (e.g., a “bowl-like” structure) configured to increase separation ofthe gaseous phase of the first mixture from the liquid phase byincreasing a surface area of the first mixture within the high-pressurevessel 110. For example, the high-pressure vessel 110 can include a bowl132 arranged within the upper region of the high-pressure vessel 110 anddefining a concave surface curved upward toward the compressor 120. Thefirst mixture can then flow downward from an outlet of the compressor120 and into the high-pressure vessel 110, where it splashes onto theconcave surface of the bowl 132. The first mixture can then splash outof the bowl 132 into the lower region of the high-pressure vessel 110and/or spill over the edges of the concave surface of the bowl 132 downinto the lower region. By enabling the first mixture to splash in andout of the bowl 132 and eventually fall downward into the lower regionof the high-pressure vessel 110, the system 100 promotes separation ofthe secondary gases from the working fluid and dissolved carbon dioxideby increasing surface area of the first mixture and thus increaseevaporation of the secondary gases across this surface area.

4.3.1 Exhaust Stream

Block S140 of the method S100 recites releasing the exhaust stream fromthe high-pressure vessel 110 via an exhaust outlet 134. As describedabove, the exhaust stream can separate from the second mixture withinthe high-pressure vessel 110 via gravity (e.g., due to differences indensity). This exhaust stream can exit the high-pressure vessel 110 viathe exhaust outlet 134 located within the upper region of thehigh-pressure vessel.

In one variation, the system 100 can include a turbocharger coupled tothe exhaust outlet 134 of the high-pressure vessel 110 and to theventuri 112. The turbocharger can include a turbo-expander 136mechanically coupled to a turbo-compressor 137 via a shared driveshaft(e.g., distinct from driveshaft 152). The turbo-compressor 137 can befluidly coupled to the venturi 112. In this variation, hot compressedgases (e.g., secondary gases) exiting the high-pressure vessel 110 canbe transferred via the exhaust outlet 134 to the turbo-expander 136. Theturbo-expander 136 can extract energy from these high-energy,high-pressure secondary gases via expansion to generate a torque on theshared driveshaft to rotate the turbo-compressor 137. Theturbo-compressor 137 can be configured to intake ambient air andcompress this air, thereby increasing pressure of the air. Theturbo-compressor 137 can then feed this compressed air to the venturi112. Therefore, by including this turbocharger, a portion of the airstream entering the venturi 112 is already pressurized above ambientpressure, thus enabling further and faster absorption of carbon dioxideinto the working fluid and minimizing energy required by the compressor120 to compress air in the first mixture.

4.4 Depressurizing the Second Mixture

Block S150 of the method S100 recites conveying the second mixture fromthe high-pressure vessel 110 through a turbine 140 configured to extractenergy from the second mixture and reduce the pressure of the secondmixture, from the second pressure at an inlet of the turbine 140 to thefirst pressure within the first pressure range at an outlet of theturbine 140, to promote desorption of carbon dioxide from the workingfluid. In particular, the system 100 can include the turbine 140 (e.g.,a Francis turbine 140) configured to receive the second mixture at afirst pressure and output the second mixture at a second pressure lessthan the first pressure. As pressure of the second mixture decreasesalong the turbine 140, the capacity of the working fluid for absorbingcarbon dioxide decreases, thus enabling separation of carbon dioxidefrom the working fluid in the liquid phase.

The turbine 140—mechanically coupled to the compressor 120 via thedriveshaft 152—can be configured to recover and recycle energy lost inthe compressor 120. For example, as pressure builds up in thehigh-pressure vessel 110 over time, the turbine 140—thermally coupled tothe high-pressure vessel 110—heats up and eventually reaches a steadystate. Once the turbine 140 reaches this steady state, any excess energyharnessed from running the second mixture through the turbine 140 can beleveraged to power the compressor 120. Therefore, the energy input bythe motor 150 in order to power the compressor 120 will decrease overtime as the turbine 140 approaches steady state, thus decreasing powerrequired to maintain operation of the system 100 and decreasingoperating costs.

The turbine 140 can be mechanically coupled to the compressor 120 andthe motor 150 via the driveshaft 152. Further, the turbine 140 can benested within both the low-pressure vessel 130 and the high-pressurevessel 110, such that an outer face of the turbine 140—including theoutlet of the turbine 140—is approximately flush with a bottom surfaceof the high-pressure vessel 110. Therefore, high-pressure high-energyfluid (i.e., the second mixture) exiting the high-pressure vessel no isautomatically drawn into the turbine 140 via gravity. At an outlet ofthe turbine 140, the resulting low-pressure low-energy fluid isautomatically released into the low-pressure vessel 130.

4.5 CO₂ Capture

Block S160 of the method S100 recites transferring the second mixturefrom the turbine 140 into the low-pressure vessel 130. In particular,once the second mixture exits the turbine 140, the second mixture can bereleased into the low-pressure vessel 130 at reduced pressures. Thelow-pressure vessel 130—encompassing the high-pressure vessel 110, thecompressor 120, and the turbine 140—can be configured to maintain thesereduced pressures and/or to further reduce pressure of the secondmixture within the low-pressure vessel 130. At these reduced pressures,the carbon dioxide separates from the working fluid in the liquid phaseto generate carbon dioxide gas distinct from the working fluid.

To increase an extent and/or rate of separation of the carbon dioxidegas from the working fluid, the low-pressure vessel 130 can implementmethods and/or techniques for cooling the working fluid within thelow-pressure vessel 130. For example, the system 100 can include a setof copper coils (i.e., a cooling jacket) surrounding the low-pressurevessel 130. Further, in this example, the low-pressure vessel 130 caninclude a first temperature sensor arranged near a top of thelow-pressure vessel 130 and a second temperature sensor arranged near abottom of the low-pressure vessel 130. The system 100 can thereforemonitor a temperature gradient across the low-pressure vessel 130 andcool the low-pressure vessel 130 via pumping refrigerant (e.g., coolwater, ethylene glycol) through the set of copper coils to maintain aparticular temperature gradient within the low-pressure vessel 130. Bymaintaining the low-pressure vessel 130 within a particular temperaturerange or maintaining a particular temperature gradient across thelow-pressure vessel 130, the system 100 enables the workingfluid—including dissolved carbon dioxide—to cool to sufficiently lowtemperatures (e.g., between 30 and 35 degrees Celsius) quickly, suchthat the carbon dioxide dissolved in the working fluid separates fromthe working fluid and exits the low-pressure vessel 130 via thecollection outlet 160 before the working fluid exits the low-pressurevessel 130 and is recycled back to the compressor 120.

Block S170 of the method S100 recites releasing carbon dioxide, desorbedfrom the working fluid, from the low-pressure vessel 130 for collection.The low-pressure vessel 130 can include a collection outlet 160 throughwhich gaseous carbon dioxide, separated from the working fluid—can exitthe low-pressure vessel 130. This carbon dioxide released from thecollection outlet 160 can be collected (e.g., bottled) and stored. Oncethe carbon dioxide is removed from the low-pressure vessel 130, theclean working fluid can be recycled back through the system 100 forcontinuous removal of carbon dioxide from atmospheric air.

5. Separated Low-Pressure and High-Pressure Vessels

In another implementation, as shown in FIG. 2, the low-pressure vessel130 and the high-pressure vessel 110 are not nested. In this variation,the low-pressure vessel 130 is fluidly coupled to the high-pressurevessel 110, and the low-pressure vessel 130, the compressor 120, thehigh-pressure vessel 110, and the turbine 140 form a loop, each fluidlycoupled to one another. In this implementation, the system 100 caninclude a singular driveshaft 152 coupled to the compressor 120, themotor 150, and the turbine 140. In this implementation, the driveshaft152 is located external the low-pressure vessel 130.

For example, in this implementation, the system 100 can include: acompressor 120 mechanically coupled to a driveshaft 152 (e.g., extendingvertically below the compressor 120) and configured to pressurize theliquid phase during transfer from the low-pressure vessel 130 into thehigh-pressure vessel 110; a turbine 140 mechanically coupled to thedriveshaft 152 (e.g., below the motor iso) and configured to extractenergy from the second mixture and to transform this energy intorotation of the compressor 120 in cooperation with the motor 150 (e.g.,to reduce power consumption of the motor 150 per unit of carbon dioxidecaptured by the system 110); a motor 150 coupled to the compressor 120and the turbine 140 via the driveshaft 152; a low-pressure vessel 130fluidly coupled to a compressor inlet 114 of the compressor 120 and to aturbine outlet 142 of the turbine 140; and a high-pressure vessel 110fluidly coupled to a compressor outlet 122 of the compressor 120 and toa turbine inlet 138 of the turbine 140. In this example, the system 100further includes: a venturi 112 configured to entrain ambient air into aworking fluid flowing from the low-pressure vessel 130 toward thecompressor 120; an exhaust outlet coupled to the high-pressure vessel110 and configured to release secondary gases (e.g., oxygen,nitrogen)—not absorbed into the working fluid at higher pressures in thesecond pressure range—from the high-pressure vessel 110; and acollection outlet 160 coupled to the low-pressure vessel 130 andconfigured to release carbon dioxide—desorbed from the working fluid atlower pressures in the first pressure range—from the low-pressure vessel120, such as by transfer into a holding tank or other storage.

5.1 Carbon Dioxide Capture

In this implementation, in which the high-pressure vessel 110 and thelow-pressure vessel 130 are not coextensive, air—including carbondioxide and the set of secondary gases—can be drawn through the venturi112 and fed to the compressor inlet 114. Simultaneously, the workingfluid can be drawn from the low-pressure vessel 130 and into thecompressor inlet 114 by the compressor 120, where the working fluid ismixed with air to form the first mixture. The first mixture—including avolume of working fluid and a volume of air dispersed within the volumeof working fluid—can then be fed to the compressor 120.

At the compressor 120, the first mixture is compressed from pressureswithin a first pressure range to pressures within a second pressurerange, pressures within the second pressure range exceeding pressureswithin the first pressure range. As pressure increases in the firstmixture, the working fluid's capacity for carbon dioxide absorptionincreases and the concentration of dissolved carbon dioxide in theworking fluid increases. Thus, after compression by the compressor 120,the first mixture includes a gaseous phase including the set ofsecondary gases and a liquid phase including the working fluid anddissolved carbon dioxide (or “carbonated working fluid”).

The first mixture can then be routed to the high-pressure vessel 110 viathe compressor outlet 122. The high-pressure vessel 110 can beconfigured to hold fluids present in the high-pressure vessel 110 atpressures within the second pressure range, such that carbon dioxideremains dissolved in the working fluid in the liquid phase. Due todifferences in densities of the liquid phase and the gaseous phase, thegaseous phase separates to an upper region of the high-pressure vessel110, while the liquid phase separates to a lower region of thehigh-pressure vessel 110. Alternatively, in one variation, thehigh-pressure vessel 110 can be configured to enable separation of thegaseous phase and the liquid phase via vortex separation.

The secondary gases of the gaseous phase can then exit the high-pressurevessel 110 through an exhaust outlet 134 coupled to the upper region ofthe high-pressure vessel 110. These heated secondary gases can then bereleased and/or collected and recycled to power the compressor 120, theturbine 140, and/or a turbocharger as described below.

The carbonated working fluid—including dissolved carbon dioxide in theworking fluid—can exit the high-pressure vessel 110 through a turbineinlet 138 coupled to the lower region of the high-pressure vessel 110.This carbonated working fluid can then be fed to the turbine 140 coupledto the turbine inlet 138. At the turbine 140, the carbonated workingfluid is expanded from pressures within the second pressure range topressures within a third pressure range (e.g., approximating the firstpressure range), pressures within the third pressure range less thanpressures within the second pressure range. As pressure decreases in thecarbonated working fluid, the working fluid's capacity for carbondioxide absorption decreases and the concentration of dissolved carbondioxide in the working fluid decreases, thereby forming a gaseous phaseof carbon dioxide distinct from the liquid phase of the working fluid.

The carbonated working fluid—including the gaseous phase of carbondioxide and the liquid phase of the working fluid—can then be routed tothe low-pressure vessel 130 via the turbine outlet 142. The low-pressurevessel 130 can be configured to hold fluids present in the low-pressurevessel 130 at pressures within the third pressure range to promotefurther desorption of the carbon dioxide from the working fluid in theliquid phase. Due to differences in densities of the working fluid andthe gaseous carbon dioxide, the carbon dioxide separates to an upperregion of the low-pressure vessel 130, while the working fluid remainsin a lower region of the low-pressure vessel 130. Alternatively, in onevariation, the low-pressure vessel 130 can be configured to enableseparation of the working fluid and the gaseous carbon dioxide viavortex separation.

The carbon dioxide can then exit the low-pressure vessel 130 through acollection outlet 160 where it can be routed to a carbon dioxideaccumulator 162 for storage. The working fluid remaining in thelow-pressure vessel 130 can then be drawn back through the compressorinlet 114 for continuous carbon dioxide capture.

5.2 Turbocharger

In one variation, the system 100 can include a turbo-expander 136coupled to the exhaust outlet 134 of the high-pressure vessel 110. Theturbo-expander 136 can be mechanically coupled to a turbo-compressor 137via a shared driveshaft (e.g., distinct from driveshaft 152), thusforming a turbocharger. The turbo-compressor 137 can be fluidly coupledto an inlet of the venturi 112. In this variation, hot compressed gases(e.g., secondary gases) exiting the high-pressure vessel 110 can betransferred via the exhaust outlet 134 to the turbo-expander 136. Theturbo-expander 136 can expand these hot compressed gases therebyreducing pressure of the gases. Simultaneously, rotation of theturbo-expander 136—driven by the exhaust stream of the high-pressurevessel 110—drives rotation of the turbo-compressor 137 mechanicallycoupled to the shared driveshaft. The turbo-compressor 137 can beconfigured to intake atmospheric air and compress this air, therebyincreasing pressure of the air. The turbo-compressor 137 can then feedthis compressed air to the inlet of the venturi 112. Therefore, byimplementing this combination of the turbo-expander 136 and theturbo-compressor 137, a portion of the air stream entering the venturi112 is already pressurized above ambient pressure, thus enabling furtherand faster absorption of carbon dioxide into the working fluid andminimizing energy required by the compressor 120 to compress air in thefirst mixture.

6. Variation: Vertical Narrow Compressor

In one variation, as shown in FIG. 5, the system 100 can be configuredto transfer heat from the atmosphere into the ground. In this variation,the system 100 can include a housing tube 170 configured to pump theworking fluid vertically below a surface of the ground to enablegeothermal heat exchange between the working fluid and the ground whichexhibits a higher heat capacity than the working fluid and air. Further,the housing tube 170 can extend to a particular depth (e.g., less than400 feet) below the surface such that the working fluid and entrainedair—forming the first mixture—can be compressed via gravity whileflowing vertically downward through the housing tube 170.

The housing tube 170 can be configured to maximize heat transfer betweenthe working fluid and the ground. For example, the housing tube 170 canbe configured to: extend below the surface of the ground to a particulardepth in order to maximize a surface area over which heat can transferbetween the working fluid and the ground; and include walls of a maximumthickness in order to minimize a distance that heat must travel from theworking fluid, through the housing tube 170, and to the ground.

For example, the working fluid can be mixed with air—including carbondioxide and the set of secondary gases—to form the first mixture. Thefirst mixture can then flow—via gravity—down the housing tube 170 from asurface of the ground toward a particular depth (e.g., 300 feet) belowthe surface. As the first mixture flows down the housing tube 170, thepressure of the first mixture increases at greater depths below thesurface, thus enabling absorption of carbon dioxide into the workingfluid. Further, the first mixture can flow past a heat exchangerconfigured to extract heat from the working fluid, thereby cooling theworking fluid and enabling (near) isothermal compression of the firstmixture. Heat extracted by this heat exchanger can be released into theground for geothermal heat exchange, thereby enabling heat transfer fromthe atmosphere into the ground.

At a bottom (i.e., the high-pressure vessel 110) of the housing tube170, the high-pressure high-energy secondary gases can separate from theworking fluid and dissolved carbon dioxide. These secondary gases can bereleased from this high-pressure vessel no via the exhaust outlet 134travelling upward through the housing tube 170. The remaining secondmixture—including the working fluid and dissolved carbon dioxide—can bepumped upward via a fluid return tube within the housing tube 170. Asthe second mixture is pumped upward through the fluid return tube 172,the pressure of the high-pressure high-energy second mixture decreasesat depths closer to the surface of the ground, thus enabling desorptionof carbon dioxide from the working fluid. Therefore, at or near thesurface of the ground, carbon dioxide can be separated from the workingfluid and collected via the collection outlet 160.

The systems and methods described herein can be embodied and/orimplemented at least in part as a machine configured to receive acomputer-readable medium storing computer-readable instructions. Theinstructions can be executed by computer-executable componentsintegrated with the application, applet, host, server, network, website,communication service, communication interface,hardware/firmware/software elements of a user computer or mobile device,wristband, smartphone, or any suitable combination thereof. Othersystems and methods of the embodiment can be embodied and/or implementedat least in part as a machine configured to receive a computer-readablemedium storing computer-readable instructions. The instructions can beexecuted by computer-executable components integrated bycomputer-executable components integrated with apparatuses and networksof the type described above. The computer-readable medium can be storedon any suitable computer readable media such as RAMs, ROMs, flashmemory, EEPROMs, optical devices (CD or DVD), hard drives, floppydrives, or any suitable device. The computer-executable component can bea processor but any suitable dedicated hardware device can(alternatively or additionally) execute the instructions.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the embodiments of the invention without departing fromthe scope of this invention as defined in the following claims.

I claim:
 1. A method comprising: mixing ambient air including carbondioxide and a set of secondary gases with a working fluid from alow-pressure vessel to generate a first mixture including a volume ofair dispersed throughout the working fluid; conveying the first mixturethrough a compressor configured to pressurize the first mixture from afirst pressure within a first pressure range at an inlet of thecompressor to a second pressure within a second pressure range at anoutlet of the compressor, the second pressure range greater than thefirst pressure range, to promote absorption of carbon dioxide present inthe volume of air into the working fluid; depositing the first mixturein a high-pressure vessel to generate: an exhaust stream including theset of secondary gases; and a second mixture including carbon dioxidedissolved in the working fluid; releasing the exhaust stream from thehigh-pressure vessel via an exhaust outlet; conveying the second mixturefrom the high-pressure vessel through a turbine configured to extractenergy from the second mixture and reduce pressure of the secondmixture, from the second pressure at an inlet of the turbine to thefirst pressure within the first pressure range at an outlet of theturbine, to promote desorption of carbon dioxide from the working fluid;transferring the second mixture from the turbine into the low-pressurevessel; and releasing carbon dioxide, desorbed from the working fluid,from the low-pressure vessel for collection.
 2. A system comprising: aventuri configured to mix ambient air with a working fluid stored in alow-pressure vessel to generate a first mixture comprising: a liquidphase comprising a volume of the working fluid; and a gaseous phasecomprising a volume of air dispersed within the volume of the workingfluid, the volume of air comprising carbon dioxide and a set ofsecondary gases; a compressor mechanically coupled to a driveshaft andconfigured to pressurize the first mixture from a first pressure in afirst pressure range at an inlet of the compressor to a second pressurewithin a second pressure range at an outlet of the compressor, thesecond pressure range greater than the first pressure range, to promoteabsorption of carbon dioxide present in the gaseous phase into theworking fluid in the liquid phase; a motor mechanically coupled to thedriveshaft and configured to drive the compressor; a high-pressurevessel configured to receive the first mixture, at the second pressure,from the compressor; an exhaust outlet configured to collect an exhauststream, including the set of secondary gases separated from the liquidphase and the gaseous phase of the first mixture, from the high-pressurevessel; a turbine inlet configured to collect a second mixture from thehigh-pressure vessel, the second mixture comprising the working fluidand dissolved carbon dioxide; a turbine mechanically coupled to thedriveshaft and configured to: reduce the second mixture exiting thehigh-pressure vessel from the second pressure at the turbine inlet tothe first pressure at an outlet of the turbine by extracting energy fromthe second mixture; promote desorption of carbon dioxide from theworking fluid; and transfer energy extracted from the second mixtureinto a torque on the driveshaft to rotate the compressor; thelow-pressure vessel configured to receive the second mixture, at thefirst pressure, from the turbine; and a collection outlet configured tocollect carbon dioxide from the low-pressure vessel.